An Iranian woman sentenced to death by stoning after she was convicted of adultery has been released from jail, a human rights group claimed last night.

Sakineh Mohammadi Ashtiani, whose plight became an international cause célèbre, was said to have been released along with her son, Sajad, her lawyer and two German journalists who were arrested over the case.

Photographs of Ms Ashtiani meeting her son were released by Iran's state-run English television channel, Press TV. They appeared to show the pair at home in Osku, in north-western Iran, and boosted her supporters' hopes that she had been released.

But footage broadcast by the station later raised doubts about whether Ms Ashtiani had actually been freed, or whether Iranian officials had merely taken her home to collect evidence against her and film a confession. In a short video clip, she was heard to say: "We planned to kill my husband."

The 43-year-old mother of two has been in prison since 2006 and faced execution by stoning for "having an illicit relationship outside marriage".

Mina Ahadi, a spokeswoman for the Germany-based Anti-Stoning Committee, which has campaigned for Ms Ashtiani's release, said: "This is the happiest day in my life. I'm very happy for her son, Sajad, who fought single-handedly and bravely in Iran to defend his mother and tell the world that she is innocent. I'm sure this day will be written in Iranian history books, if not the world's, as a day of victory for human rights campaigners.

"We have got news that they are free. We are waiting for another confirmation... then we will be 100 per cent sure."

There was no official statement about Ms Ashtiani by authorities in Tehran, and the Foreign Office in London said it was awaiting clarification. But Franco Frattini, the Italian Foreign Minister, said her reported release marked "a great day for human rights". "Iran has made the gesture of understanding and clemency that we were hoping for, and it did so using its prerogative as a sovereign state," he added.

"It is a decision that merits strong praise and satisfaction. We take note of this in the knowledge that the prospect for dialogue with Iran also on human rights can resume in a spirit of renewed mutual confidence."

There was an international outcry in the summer when Ms Ashtiani's sentence became public knowledge. Brazil's President, Luiz Inácio Lula da Silva, offered to give her asylum in his country, while the US Secretary of State, Hillary Clinton, urged Tehran to respect the fundamental freedoms of its citizens. In Britain, the Foreign Office minister, Alistair Burt, condemned the laws used against her as "medieval".

Iran's conservative Kayhan newspaper reserved its ire for the French First Lady, Carla Bruni-Sarkozy, calling her a "prostitute" after she attacked the Tehran regime over the sentence.

The news of Ms Ashtiani's possible reprieve came a day after another Iranian woman, Khadijeh Jahed, also known as Shahla, was hanged at dawn in jail, with her son pushing the stool from beneath her feet. The decision to carry out Ms Jahed's execution, which was also the focus of worldwide outrage, appeared to indicate that the Iranian regime was maintaining a tough stance despite a UN General Assembly committee criticising the country's "serious ongoing human rights violations" and "pervasive gender inequality and violence against women".

Ms Ashtiani's lawyer, Javid Houtan Kian, was arrested in Tabriz in September with two German journalists who were interviewing her son.

The Germans, who worked for the newspaper Bild Am Sonntag and had entered Iran on tourist visas, are accused of spying.